1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device, more particularly, to a method of manufacturing a storage electrode of a capacitor having an extended effective surface area.
2. Description of the Related Art
In a semiconductor memory device such as a dynamic random access memory (DRAM) having a plurality of memory cells, each cell must include as base components an access transistor and a storage capacitor. However, the recent high integration trend of semiconductor devices inevitably involves a reduction in size of each cell area, thereby resulting in a reduction in the area occupied by the capacitor.
Many attempts have been made to realize capacitors that can obtain a desired capacitance from a given small area.
The area of a capacitor and the dielectric constant of dielectric layers used to form the capacitor directly affect the capacitance value. The area of capacitor represents the effective area of dielectric layer between storage electrode and plate electrode, and an increase in the effective area of dielectric layer can increase capacitance. Meanwhile, dielectric layers such as Ta2O5 or Al2O3 are developed to replace conventional nitride-oxide (NO) dielectric layers, and layers having higher dielectric, such as (Ba, Sr)TiO3 (BST), have also been proposed.
Metal electrodes are necessary for adopting high dielectric layers, but the use of these metal electrodes is accompanied by technical difficulties. Also, there are some technical limits to adopting capacitor using polysilicon electrode and Ta2O5 or Al2O3 dielectric layer as design rule of semiconductor devices decreases to 0.15 μm.
Accordingly, a need exists for a method of manufacturing a storage electrode of a capacitor having an extended effective surface area.